Heavy electrons and non-Fermi liquids, the early times

In retrospect, the observation of the unusual electronic properties of CeAl3 at very low temperatures was a major step in a new direction, away from the conventional concepts for the understanding of the ground state of metals. The new perspectives took their time to be accepted, but the discovery of superconductivity involving conduction electrons with large effective masses, and the subsequent recognition of its unconventional character, served as eye-openers. This brief review is aiming at covering some of the major aspects of this development before the discovery of high-Tc superconductivity in cuprates.